1. Field of the Invention
The present invention relates to containers for storing and/or transporting materials. More particularly, the present invention relates to collapsible containers that may be employed to transport bulk materials including, but not limited to, hazardous materials. Still more particularly, the present invention relates to collapsible storage containers and protective covers therefor.
2. Description of the Prior Art
Metal containers are generally used to store and transport bulk materials, particularly hazardous materials. These metal containers are expensive to purchase or, more often, to rent. They are fairly large and therefore require a considerable amount of space to maintain on site. That required space could be considerable, dependent upon the amount of material that must be stored and/or transported. Alternatively, bag containers have been employed. Such bags take up much less space when not in use. However, such bags are of insufficient physical characteristics for transport purposes. That is, they are generally not tough enough to stand up to the rigors of movement by mechanical devices such as forklifts, accidental drops into cargo holds, stacking, and the like.
In order to overcome the limitations associated with flexible bags and rigid metal boxes, a collapsible container has been developed. The best of the collapsible containers suitable for the storage and/or transport of bulk materials including hazardous materials is one offered by U.F. Strainrite, Inc. of Lewiston, Me., the assignee of the present invention. The Strainrite collapsible storage container is described in U.S. Pat. No. 6,000,604, issued Dec. 14, 1999, and in U.S. Pat. No. 5,323,922, issued Jun. 28, 1994. The contents of both of those patents are incorporated herein by reference.
The collapsible container offered by Strainrite is based upon a multi-walled box of the type shown in FIG. 1. In the commercial configuration shown in that drawing, the container 10 includes a base 20 and coupled to walls 12, 14, 16, and 18. Each wall is formed of a sandwich of tough woven flexible material encasing a rigid member, such as a corrugated board. The two outer woven materials are coupled together to retain the rigid member therebetween. Opposing walls 12 and 18 each includes an integral flap 26 made of the flexible material and preferably omitting the rigid member. Wall 14 includes a short integral flap 24 and wall 16 includes integral covering flap 22. As indicated in U.S. Pat. No. 6,000,604, flap 22 is designed to act as a single complete covering that ensures material within the container 10 will not escape under expected transport conditions. A supplemental retaining bag 32 may also form part of the container 10, particularly when the material 50 to be retained therein is relatively fluid.
The walls 12, 14, 16, and 18 of the prior container 10 are coupled together and arranged so that they may be collapsed adjacent to one another while remaining coupled together in a substantially flat configuration when nothing is retained therein. This combination of elements ensures an easily stored container that takes up much less space than the metal containers. The inclusion of the captured rigid members forming part of the walls of the container 10 ensure that when in use, the container 10 is sufficiently rigid to stand up to the rigors of expected operation of this type of container. Such containers are also substantially less expensive than the conventional metal containers.
While the collapsible container described in U.S. Pat. No. 6,000,604 is a great improvement over the storage/transport containers of the prior art, there are two ways in which the container described in that patent can be improved. First, the retaining bag 32 is suggested as a suitable means for retaining wet materials. It is indicated that the bag may be fabricated of a variety of any of the non-metallic materials woven polypropylene, waterproofed woven polypropylene, polyethylene, high-density polyethylene, nylon, or combinations thereof. Unfortunately, those materials specifically suggested fail to enable use of the container 10 for the purpose of holding relatively hot materials including, but not limited to, spent catalysts.
In the field of chemical processing, a fairly standard technique for accelerating and/or facilitating chemical reactions includes the introduction of catalysts and perhaps the application of heat. The catalysts provide sites for reactions to occur. However, they generally have limited useful lives and must therefore be replaced to ensure optimal efficiency in the chemical reaction process. The process of removing the catalyst generally involves a dumping from a reactor into a container. That container must be fabricated of a material sufficient to withstand the temperatures ordinarily used in such reactions. Those temperatures can be as much as 750xc2x0 F. The materials suggested for the bag 32 as well as the walls 12, 14, 16, and 18 of container 10 could only reasonably be expected to safely retain materials at temperatures of about 200xc2x0 F. Given the quantity of catalyst to be removed, it can take several weeks for cool-down to a temperature suitable for introduction into container 10. As a result, the container user would be required to store the spent catalyst for that period of time before then placing it in the container. That is not a desirable situation. Instead, it would be preferable to have a collapsible container capable of retaining materials including, but not limited to catalysts, at elevated temperatures. Such a container would save its user considerable cost by allowing that user to employ the container when convenient, rather than waiting for weeks for material cool down. Given the considerable rental fees associated with metal containers, a less-expensive collapsible container could be employed when desired.
Relatedly, it is important that when catalyst in particular is to be retained in the container, the possibility of further chemical reactions occurring be substantially minimized. Although catalysts are typically removed from reactors when the reaction efficiency declines, there nevertheless remains some reactivity. Such reactivity can be enhanced under a variety of atmospheric conditions. One of those conditions is the availability of reactive gases such as oxygen. The availability of oxygen to the catalyst can cause continuing reactions that can produce hazardous offgassing as well as increased temperatures within the container. Increased temperatures can cause an acceleration of the reaction, causing a greater increase in temperature, and so on. For that reason, it is important that the container used to retain reaction catalysts in particular be substantially impervious to reactive gases such as oxygen. U.S. Pat. No. 6,000,604 fails to disclose such a requirement as part of the design of the container 10.
A second limitation of the collapsible container 10 of the prior art is the cover design. Although cover 22 provides an effective seal to prevent the bulk material within from escaping the container 10, it may be inadequate to block weather conditions from entering from the outside. In particular, bulk material containers are often left in open storage locations. They therefore experience precipitation such as rain, sleet, snow, and the like. The design of container 10 as shown particularly in FIG. 6 of U.S. Pat. No. 6,000,604 renders the container 10 susceptible to water seepage into the container, particularly at the upper corners of the container 10. Such seepage may potentially cause damage to the rigid member forming the structural member of the walls of the container. Moreover, the water seepage may potentially have an adverse effect on the bulk material stored therein, dependent upon the characteristics of that material.
Therefore, what is needed is a collapsible container for the storage and transport of bulk materials suitable for retaining materials at elevated temperatures. What is also needed is a collapsible container that minimizes the introduction of reactive components to the contents of the container. Further, what is needed is a storage container including an effective cover to minimize the introduction of fluids from the exterior to the interior of the container.
It is an object of the present invention to provide a collapsible container for the storage and transport of bulk materials suitable for retaining materials at elevated temperatures. It is also an object of the present invention to provide a collapsible container that minimizes the introduction of reactive components to the contents of the container. Further, it is an object of the present invention to provide a storage container including an effective cover to minimize the introduction of fluids from the exterior to the interior of the container.
These and other objects of the present invention are achieved by introducing a protective liner to a storage container, such as a collapsible, semi-rigid storage container. The protective liner is designed to be retained within the interior of the container and, for collapsible containers, with minimal impact on the collapsing method. The liner is made of a material that is a barrier to reactive gases, such as oxygen. It is also resistant to deformation or failure under relatively high temperatures when compared the temperature resistance of the prior optional bag described in the referenced prior patent. Additionally, the material of the liner of the present invention is relatively flame-resistant. One example of a material suitable for this purpose is a co-extrusion of polypropylene/nylon/polypropylene xe2x80x9chot fill.xe2x80x9d This blend offers high-temperature resistance, water repellant, and a strong oxygen barrier, particularly when compared to other polymeric blends. It is to be noted, however, that other materials may be suitable for this application provided they exhibit similar isolation characteristics.
The introduction of the protective liner of the present invention provides the means for storing and transporting spent catalysts. In particular, using a process in which a coolant means, such as dry ice or other suitable cooling medium, and the liner are placed within the container, such as the collapsible container of U.S. Pat. No. 6,000,604, relatively hot catalyst may be retained. First, the protective liner is placed into the semi-rigid container and the coolant means is placed into the liner. It is to be noted that the coolant means may have its own separate retainer, such as a liner, to isolate it from the bulk material to be shipped. The spent catalyst is then placed within the container in direct or substantially direct contact with the coolant means. It is to be noted that the catalyst may be at an elevated temperature defined by the limitations of the liner""s characteristics, including, but not limited to, a temperature of about 200xc2x0 F. The liner may then be closed and a layer of coolant placed on the top of the closed liner. The container is then closed and the container moved to a desired location. The introduction of the coolant aids to accelerate cooling of the spent catalyst while the liner ensures that oxygen is prevented from contacting the catalyst once the container is closed. The characteristics of the liner substantially minimize that contact. Prior to closing the container, a nitrogen probe line may be inserted into the container to introduce a nitrogen coolant to aid further in the accelerated cooling of the contained catalyst.
The addition of the impervious liner to a storage container permits retention of bulk materials that previously could not be easily retained at relatively high temperatures in semi-rigid containers. Moreover, the introduction of such a liner to a collapsible semi-rigid container expands the capability of such a container. As previously noted, collapsible containers have particular advantages over existing metal containers and simple plastic bags. Those advantages are enhanced when that type of container includes the liner of the present invention to enable retention of high-temperature reactive materials.
A separate improvement of the container of the present invention is the application of a dedicated weather-blocking cover. The cover of the present invention supplements the function of the existing lid disclosed in U.S. Pat. No. 6,000,604. In particular, it is a flexible unitary structure that may be fabricated of the same material used to form the interior and exterior layers of the sandwich walls of the collapsible container. The cover structure may be formed integrally with the cover flap 22 of the container 10 of FIG. 1. Alternatively, it may be a separate component including a plurality of grommets or burn holes through which flexible tie-downs may be used to secure it to the walls of the container. Preferably, the weather-blocking cover of the present invention is formed of sufficient dimensions to ensure that it passes over all upper corners of the container so that it may be retained in place on the walls. That arrangement eliminates a direct interface between the upper corners of the container and the surrounding environment. Addition of the supplemental blocking cover permits outdoor storage of a filled container or a plurality of stacked containers, for an extended period.
The introduction of either one or both of the impervious liner and the blocking cover improve the storage capability of any container, but particularly a collapsible container of the type described in U.S. Pat. No. 6,000,604. Such a container may be used to provide a cost-effective means for owning a plurality of containers that can hold and transport bulk materials including spent catalyst. It is capable of retaining materials including, but not limited to, self-heating, solid, inorganic sulfides, sulfurs, and the like that may be classified as class 4.2 under the International Maritime Dangerous Goods code. Further, a single container can be used to replace a plurality of 55-gallon drums. While made of materials that make it lightweight when empty, the lined collapsible container may readily retain up to 3000 lbs. of bulk material.
These and other advantages of the present invention will become more apparent upon review of the following detailed description and the accompanying drawings.